Late Pleistocene glaciations in southern East Sayan and detection of MIS 2 terminal moraines based on beryllium ( 10 Be) dating of glacier complexes
Résumé
Analysis and summary of publications on southern East Sayan, eastern Tuva, and northern Mongolia have shown that the late Pleistocene glaciation covered a large area and had a complicated dynamics of glacier advance and retreat. Starting with MIS 5, the Todza Basin and, partly, the Oka Plateau, Azas Volcanic Plateau, Mondy Basin, and river valleys in southern East Sayan were periodically covered with ice. The thickness of ice in the eastern Todza Basin was 700 m, on the Azas Volcanic Plateau it reached 300–600 m, and in the valleys of southern East Sayan it is estimated as 700–800 m. The thickness of ice in the Mondy Basin was 300–350 m. Geological and geomorphological studies and isotope surface exposure dating (10 Be method) of boulders from terminal moraine complexes have provided evidence for extensive MIS 2 glacier advance in the Mondy Basin and in the Sentsa, Jombolok, and Sailag river valleys (southern East Sayan). The average age of exposure for three groups of samples is 14, 16, and 22 ka